Phytoremediation Site Research Articles

The impact of tritium phytoremediation on plant health as measured by fluorescence

Phytoremediation, using plants for soil, sediment, or water contaminant clean-up, is an established technology dependent on plant health. Tritium (3H), a radioactive isotope of hydrogen that is generally found in the environment as tritiated water (HTO), is a low-level beta emitter with a half-life of 12.32 years. Chlorophyll fluorescence (CF) for monitoring risk assessment of tritium to plant health was conducted at the Tritium Irrigation Facility (TIF) located on the US Department of Energy's Savannah River Site (SRS) near Aiken, SC. Two fluorometers were evaluated in conjunction with phytoremediation at the 25 –acre TIF where tritiated groundwater is being spray–irrigated on a mixed coniferous/deciduous forested watershed as a means of reducing tritium release to a nearby stream that serves as a tributary to the Savannah River. Tritium activity in irrigated water averaged 104 + 42 pCi mL-1 during the 2003 project. Fluorescence parameters measured by the two fluorometers were well correlated with each other (p < 0.0001). Tritium in water respired from oak leaves ranged up to 1845.13 pCi ml−1 and 2138.22 pCi ml−1 in pine needles. Trees in both the test and control sites were approximately 15 years old. Here we demonstrated that fluorescence parameters provide an effective way to estimate the impact of HTO on plant health in a noninvasive, extremely rapid, and cost-effective manner. In the current study applying fluorometry, plants within the TIF phytoremediation site exposed to the site tritiated water were not significantly impacted by the tritium phytoremediation based on CF parameters as compared to the control, a nascent non-irrigated site.

Breeding polyploid &lt;i&gt;Populus&lt;/i&gt;: progress and perspective

<i>Populus</i> is a genus of 25−30 species of deciduous flowering plants in the family Salicaceae, which are primarily planted in short-rotation planations for producing timber, pulpwood, wooden products as well as bioenergy feedstock; they are also widely planted in agricultural fields and along roadsides as shelter forest belts for windbreak, decoration, and reduction of pollutants and noise. Moreover, their fast-growth and good adaptation to marginal lands enable them to provide some critical ecosystem services at various phytoremediation sites for land restoration and reclaimation. Thanks to their important roles, breeding for fast growing poplar trees has been one of the most important objectives for nearly a century. One of the most demonstrated, documented achievements in this aspect is polyploid breeding, especially triploid breeding. This paper critically reviews the various techniques used in inducing triploid plants, including natural 2n formation, artificial induction of 2n male and female gemmates through chemical or physical treatments, trait characterization of the triploid and tetraploid breeding populations, unveiling the molecular mechanisms underpinning the significantly improved traits, and identification and selection of the best triploid progenies. This review also recapitulated the challenges and strategies facing the future of triploid breeding in <i>Populus</i>, including amelioration of 2n gamete induction techniques and efficiency, selection of the best parents and identification of the best progrenies, utilization of the huge amount of genomic, transcriptomic, proteomic, metabolomic, and other omics data for selecting parents for improving target traits.

Establishment of willows using the novel DeValix technique: ecological restoration mats designed for phytotechnologies

Successful willow (Salix spp., hybrids and cultivars) establishment is a major determinant of their effectiveness when grown for phytotechnologies. Vertically-planted hardwood cuttings have been shown to produce adequate willow growth and survival, although site conditions at phytoremediation installations can make vertical planting methods unsuitable. The DeValix willow mat restoration technique was designed and tested as an alternative horizontal planting method that can be installed by hand in a variety of environmental applications. The DeValix technique was evaluated by testing five willow clones (“Millbrook”; “Sherburne”; “SX61”; “SX67”; “Tully Champion”) grown at two phytoremediation sites (Ontonagon, MI; Manitowoc, WI) for the 2019 growing season. Differences in survival and growth were tested among sites, genotypes, and their interactions. Stem height, diameter, and number of stems per mat were compared to identify clones with greater establishment success and higher phytoremediation potential. Results demonstrated significant effects of site (p < 0.0001) and clone (p < 0.0001) on shoot number. Additionally, the site × clone interaction significantly affected stem height (p = 0.0045) and diameter (p = 0.0166). Stem density ranged from 95,000 to 212,000 stems per hectare, indicating the DeValix technique is a viable establishment method for environmental applications, including phytoremediation and shoreline stabilization. Novelty statement This research analyzes the establishment success of the DeValix technique, a novel horizontal planting method for willow cultivars, and evaluates the DeValix technique as an alternative to other horizontal techniques and traditional vertical planting methods currently used in environmental applications. Results from this study add to the current knowledge of planting techniques and assesses the use of the DeValix technique for planting willow cultivars that are currently being tested in several phytotechnology systems.

Identification of degrader bacteria and fungi enriched in rhizosphere soil from a toluene phytoremediation site using DNA stable isotope probing

Improved knowledge of the ecology of contaminant-degrading organisms is paramount for effective assessment and remediation of aromatic hydrocarbon-impacted sites. DNA stable isotope probing was used herein to identify autochthonous degraders in rhizosphere soil from a hybrid poplar phytoremediation system incubated under semi-field-simulated conditions. High-throughput sequencing of bacterial 16S rRNA and fungal internal transcribed spacer (ITS) rRNA genes in metagenomic samples separated according to nucleic acid buoyant density was used to identify putative toluene degraders. Degrader bacteria were found mainly within the Actinobacteria and Proteobacteria phyla and classified predominantly as Cupriavidus, Rhodococcus, Luteimonas, Burkholderiaceae, Azoarcus, Cellulomonadaceae, and Pseudomonas organisms. Purpureocillium lilacinum and Mortierella alpina fungi were also found to assimilate toluene, while several strains of the fungal poplar endophyte Mortierella elongatus were indirectly implicated as potential degraders. Finally, PICRUSt2 predictive taxonomic functional modeling of 16S rRNA genes was performed to validate successful isolation of stable isotope-labeled DNA in density-resolved samples. Four unique sequences, classified within the Bdellovibrionaceae, Intrasporangiaceae, or Chitinophagaceae families, or within the Sphingobacteriales order were absent from PICRUSt2-generated models and represent potentially novel putative toluene-degrading species. This study illustrates the power of combining stable isotope amendment with advanced metagenomic and bioinformatic techniques to link biodegradation activity with unisolated microorganisms. Novelty statement: This study used emerging molecular biological techniques to identify known and new organisms implicated in aromatic hydrocarbon biodegradation from a field-scale phytoremediation system, including organisms with phyto-specific relevance and having potential for downstream applications (amendment or monitoring) in future and existing systems. Additional novelty in this study comes from the use of taxonomic functional modeling approaches for validation of stable isotope probing techniques. This study provides a basis for expanding existing reference databases of known aromatic hydrocarbon degraders from field-applicable sources and offers technological improvements for future site assessment and management purposes.

Impact of heavy metal ions on the simultaneous saccharification and fermentation of formosan alder biomass to form lactic acid

Formosan alder (Alnus formosana) is a fast-growing, adaptable, pioneer native tree species in Taiwan, and it is particularly suitable for reforestation. In this study, steam-exploded Formosan alder biomass was employed to investigate lactic acid production by simultaneous saccharification and fermentation (SSF) in the presence of different heavy metals. Impacts of added heavy metals on saccharification processing were investigated. In the presence of 1410 mg Cr6+/L, negative impacts were observed for SSF. The same level of Cr6+ adversely affected fermentation by Lactobacillus casei and L. acidophilus compared to the blank controls. Positive impacts for SSF by Cd2+ were demonstrated with 108 mg Cd2+/L, and the same conditions favored fermentation by L. casei and L. acidophilus. No impacts for SSF by Pb2+ up to 6830 mg Pb2+/L were found for both Lactobacillus strains. This study demonstrates that SSF for production of lactic acid from Formosan alder biomass was able to tolerate a wide range of heavy metal concentration regimes. Hence, this study provides an alternative use for biomass harvested from phytoremediation sites. Such biomass can be used as sustainable regenerative biomaterial, and thereby it can further enhance the benefits of environmental remediation.

Conversion of heavy metal-containing biowaste from phytoremediation site to value-added solid fuel through hydrothermal carbonization.

In this study, heavy metal-containing sunflower residues obtained from a phytoremediation site were hydrothermally carbonized at 160-260°C. The properties of hydrochar thus produced were evaluated with respect to its potential as solid fuel. The results confirmed that hydrothermal carbonization (HTC) reduced the concentration of heavy metals in hydrochars, with the concentration lower than the maximum permissible level of domestic standards for bio-solid refuse fuel. Higher HTC temperatures resulted in improved energy-related properties of the hydrochar (i.e., coalification degree, fuel ratio, and higher heating value); however, HTC temperatures between 200 and 220°C were deemed suitable for energy retention efficiency. Furthermore, as hydrochar contains low nitrogen and ash content, it can be considered as a clean energy source. The results of this study suggest a sustainable approach to the disposal and effective utilization of contaminant-containing biowastes. Moreover, this study suggests linking biomass cultivation for phytoremediation and converting the phytoremediated biomass into value-added solid fuel.

Helianthus annuus based biodiesel production from seed oil garnered from a phytoremediated terrain

Dependence on the exhaustible fossil fuels exhibited the urgent need for the development of alternative energy production based on green chemistry methods. Biodiesel production marks a green product produced from a variety of bio-entities. Current investigation is an account of the first time exploration of the biodiesel production from the seeds of sunflower (Helianthus annuus) previously garnered at a phytoremediation site. Sunflower crop has been grown for the accumulation of heavy metals at a contaminated site, later on such plants were utilised for biodiesel production via transesterification signifying a duality in achieving the purpose of environmental detoxification in addition to energy production. Biodiesel production based on the ethanolysis expressed an augmented transformation of up to 96% with simultaneously occurring inconsequential reactions. The prepared biodiesel was analysed for the presence of compounds and functional group through gas chromatography–mass spectrometry (GC–MS) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, the derivation of other products, e.g. ethyl oleate can find a potential utilisation in the pharmaceutical industry associated with the making of drugs. Relevant and apropos upgradation of the sunflower seed oils can result in the favourable biofuels. Current research is the indicative of successful use of phytoremediated crops for gaining environmental integrity.

Heavy metal accumulation and distribution in Phragmites australis seedlings tissues originating from natural and urban catchment.

The retention of heavy metal (HM) was studied in root and rhizomes (BLG), stems (ST), and leaves (LF) of Phragmites australis (common reed) seedlings collected from different locations, differing in the scale of anthropogenic interference. The analysis includes the reference samples of sediments in uncontaminated lake Garczonki and contaminated roadside ditch in Cieplewo. The concentrations of Zn, Cu, Pb, Cd, Ni, and Cr were analyzed in plant tissues and sediments using the atomic absorption spectrometry and inductively coupled plasma mass spectrometry. The general assessment of sediments collected in the Garczonki lake showed a good environmental status; while in the roadside ditch in Cieplewo, the sediments were considerably polluted with HM. In the first stage of plant growth, all of the analyzed HMs are mainly inhibited by BLG system. The decreasing trend of elements was as follows: BLG > ST > LF. The organs followed different decreasing trends of HM concentration; the trend Zn > Cu > Ni > Cr > Pb > Cd was found in ST and LF for the Garczonki lake seedlings and for BLG and LF for the roadside ditch in Cieplewo seedlings. Zn showed the highest concentration, while Cd the lowest concentration in each of the examined organs. The bioaccumulation factor indicated the higher mobility of HM in seedlings in the Garczonki lake than in the roadside ditch in Cieplewo. The morphological studies suggest the good state and health of seedling from both sites; however, the reduction of root hair surface was observed for the roadside ditch seedlings. The anatomical studies present changes in the size of the nucleus and count of chloroplasts in LF. No reaction on HM contamination sediments in the seedlings from the roadside ditch in Cieplewo in the aerenchyma was noted. Potentially, both types of seedlings can be used to decontaminate environments rich in HM. However, the level of HM absorbed by seedlings (in the first stage of growth) should be considered due to the behavior in the target phytoremediation site.

Quantification of toluene phytoextraction rates and microbial biodegradation functional profiles at a fractured bedrock phytoremediation site

This field study evaluated the efficacy of a mature hybrid poplar phytoremediation system for the remediation of toluene in a fractured bedrock aquifer site. Phytoextraction activity of the trees and the ecology and biodegradation potential of root-colonizing bacteria that ultimately influence how much toluene is transported from the roots and phytoextracted to the aboveground point of measurement were explored. Peak-season toluene mass removal rates ranging from 313 to 743 μg/day were quantified using passive in planta contaminant sampling techniques and continuous heat dissipation transpiration measurements in tree stems. Root bacterial microbiome structure and biodegradation potential were evaluated via high-throughput sequencing and predictive metagenomic functional modelling of bacterial 16S rRNA genes in roots. Poplar roots were colonized mostly by Proteobacteria, Actinobacteria, and Bacteroidetes. Distinct, more uniform communities were observed in roots associated with trees planted in the toluene source area compared to other areas, with differences apparent at lower taxonomic levels. Significant enrichment of Streptomyces in roots was observed in the source area, implicating that genus as a potentially important poplar endophyte at toluene-impacted sites. Moreover, significantly greater aerobic toluene biodegradation capacity was predicted in these roots compared to other areas using taxonomic functional modelling. Together with passive sampling, the molecular results provided supporting evidence of biodegradation activity in the source area and contextualized the detected phytoextraction patterns. These results support the application of phytoremediation systems for aromatic hydrocarbons in environments with complex geology and demonstrate field-validated monitoring techniques to assess phytoextraction and biodegradation in these systems.

Effect of particulate organic matter fractions on the distribution of heavy metals with aided phytostabilization at a zinc smelting waste slag site

Particulate organic matter (POM) significantly affects the distribution of heavy metals in contaminated soil. However, the effect of POM on the fate of heavy metals during in situ-aided phytostabilization of waste slag is unclear. The objective of this study was to investigate the distributions of heavy metals such as Cu, Pb, Zn, and Cd in the POM fractions at a zinc smelting waste slag site under in situ-aided phytostabilization after five years. The results showed that the litters and residues of four plants―Arundo donax, Broussonetia papyrifera, Cryptomeria fortunei, and Robinia pseudoacacia―decomposed to form different POM size fractions. The percentage of the 0.05–0.25 mm POM size fraction was the highest, followed by the >1 mm and 0.5–1 mm POM size fractions, and that of the 0.25–0.5 mm POM size fraction was the lowest. The masses of POM derived from the four plants were in the following order: C. fortunei > B. papyrifera > A. donax > R. pseudoacacia. The contents, enrichment coefficients, and mass loads of heavy metals such as Cu, Pb, Zn, and Cd in the POM increased with decreasing POM size, and those in the 0.05–0.25 mm POM size fraction were the highest. The mass load of heavy metals in the POM occurred in the following order: Cu > Cd > Zn > Pb. The surfaces of the POM with coarser and smaller size fractions were smoother and rougher, respectively, and the smaller POM size fractions had larger specific surface areas. The main functional groups in the different POM size fractions were –COOH, –OH, CO, CC, C–H, Si–O, and –CH3. The POM fractions played a significant role in determining the distribution of heavy metals in the revegetated waste slag. These findings have important implications for aided phytostabilization, which significantly influences the fate and speciation of heavy metals at the phytoremediation site.

Ecosystem services of poplar at long‐term phytoremediation sites in the Midwest and Southeast, United States

AbstractShort rotation woody crops (SRWCs) including Populus species and their hybrids (i.e., poplars) are ideal for incorporating biomass production with phytotechnologies such as phytoremediation. To integrate these applications, 15 poplar plantings from nine long‐term phytoremediation installations were sampled from 2012 to 2013 in the Midwest (Illinois, Iowa, Wisconsin) and Southeast (Alabama, Florida, North Carolina) United States. In this review, we report summary results of this sampling and how performance at each site compared with comparable phytoremediation systems in the literature. We review significant genotypic differences from each planting within the context of provisioning (i.e., biomass production) and regulating (i.e., carbon sequestration) ecosystem services and how they relate to the need for a cleaner environment during times of accelerated ecological degradation. Overall, the contaminated poplar sites provided these ecosystem services comparable to noncontaminated poplar sites used for bioenergy and biofuels feedstock production. For example, phytoremediation trees at the Midwestern sites had biomass values ranging from 4.4 to 15.5 Mg ha−1 y−1, which was ~20% less relative to bioenergy trees (p = .0938). Results were similar for diameter and carbon, with some genotype × environment interactions resulting in phytoremediation trees exhibiting substantially greater growth and productivity (i.e., +131% at one site). As illustrated in the current review, phytoremediation success can be increased with the identification and deployment of genotypes tailored to grow well and tolerate a broad diversity of contaminants (generalists) (i.e., ‘DN34’, ‘NM6’, ‘7300501’) versus those that significantly outperform their counterparts under unique site conditions (specialists) (i.e., ‘220‐5’, ‘51‐5’, ‘S13C20’).This article is categorized under: Concentrating Solar Power &gt; Climate and Environment Bioenergy &gt; Economics and Policy Bioenergy &gt; Science and Materials

Reaction mechanism of arsenic capture by a calcium-based sorbent during the combustion of arsenic-contaminated biomass: A pilot-scale experience

Large quantities of contaminated biomass due to phytoremediation were disposed through combustion in low-income rural regions of China. This process provided a solution to reduce waste volume and disposal cost. Pilot-scale combustion trials were conducted for in site disposal at phytoremediation sites. The reaction mechanism of arsenic capture during pilot-scale combustion should be determined to control the arsenic emission in flue gas. This study investigated three Pteris vittata L. biomass with a disposal capacity of 600 kg/d and different arsenic concentrations from three sites in China. The arsenic concentration in flue gas was greater than that of the national standard in the trial with no emission control, and the arsenic concentration in biomass was 486 mg/kg. CaO addition notably reduced arsenic emission in flue gas, and absorption was efficient when CaO was mixed with biomass at 10% of the total weight. For the trial with 10% CaO addition, arsenic recovery from ash reached 76%, which is an ∼8-fold increase compared with the control. Synchrotron radiation analysis confirmed that calcium arsenate is the dominant reaction product.

Foliar litters: Sources of contaminants in phytoremediation sites by returning potentially toxic metals (PTMs) back to soils

Phytoremediation is regarded as one of the most cost-effective and environmentally friendly strategies for potentially toxic metals (PTMs) contaminated soil remediation. However, uncertainties still existed about the contribution of foliar litter on metal accumulation and mobility in phytoremediation sites. Thus, in this study, fallen leaves, decomposed leaves, and soils at different depths (i.e., 0-5 and 5-10 cm) were collected from a phytoremediation site near a Zn smelter factory. Metals content and mobility were evaluated. Results indicated that upper-layer soils (0-5 cm) were higher in the electrical conductivity (EC) and soil organic matter (SOM) content than the deeper-layer soils (5-10 cm). However, the pH was relatively lower in the upper-layer soils. Fallen leaves were sources of metals in the phytoremediation site, and significantly high amounts of Cd (16.08 ± 0.21 mg kg-1) and Zn (1130.30 ± 60.10 mg kg-1) were found in the decomposed leaves. Metals in the upper-layer soils demonstrated higher accumulation and mobility than the deeper-layer soils. Moreover, the accumulated metals in leaves would gradually return to the soil as the contents of extractable metals increased with the rising decomposition degree of leaves (i.e., cold-water extraction < 80 °C hot water extraction < 1 M HCl extraction). Results from this research are helpful for the guidance of phytoremediation site management.

Anaerobic digestion as an alternative disposal for phytoremediated biomass from heavy metal contaminated sites

It is desirable to establish an environmentally benign platform for disposing biomass from the phytoremediation process while recovering energy is of importance. To this end, the biochemical methane potential (BMP) tests were conducted using four different biomass samples (i.e., sunflower: Helianthus annuus) that were obtained from the different remediation sites. In particular, this study laid great emphasis on evaluating the inhibition for the anaerobic digestion (AD) process induced by endogenous heavy metal (Cd, Cu, Ni, Pb, and Zn) content in biomass. Despite the high levels of heavy metal contents (Cd: 58.4, Cu: 23.0, Ni: 2.01, Pb: 9.88, and Zn: 146 mg kg−1) in the substrate for the AD process, the overall performance was comparable relative to the case of the references. Therefore, this study signified that the inhibition derived from heavy metals was nearly negligible, which suggested that biomass from the phytoremediation site could be used as a substrate for the AD process.

Long-term performance of anaerobic digestion for crop residues containing heavy metals and response of microbial communities

In order to investigate the long-term stability on the performance of the anaerobic digestion process, a laboratory-scale continuous stirred-tank reactor (CSTR) was operated for 1100 days with sunflower harvested in a heavy metal contaminated site. Changes of microbial communities during digestion were identified using pyrosequencing. According to the results, soluble heavy metal concentrations were lower than the reported inhibitory level and the reactor performance remained stable up to OLR of 2.0g-VS/L/day at HRT of 20days. Microbial communities commonly found in anaerobic digestion for cellulosic biomass were observed and stably established with respect to the substrate. Thus, the balance of microbial metabolism was maintained appropriately and anaerobic digestion seems to be feasible for disposal of heavy metal-containing crop residues from phytoremediation sites.

New mutualistic fungal endophytes isolated from poplar roots display high metal tolerance.

This study aimed to isolate, identify, and characterise metal-tolerant fungi colonising poplar roots at a metal-contaminated phytoremediation site. Poplar roots were colonised by arbuscular mycorrhizal, ectomycorrhizal, and endophytic fungi, and the species were determined by ITS molecular analyses. Eight different isolates were successfully isolated into pure culture. Three isolates belonging to the Helotiales (P02, P06) and the Serendipita vermifera species (P04) were highly tolerant to metals (Cd, Zn, Pb, and Cu) compared to the mycorrhizal Hebeloma isolates. The three isolates degraded complex carbohydrates, such as xylan and cellulose, indicating that they could partially degrade root cell walls and penetrate into cells. This hypothesis was confirmed by further in vitro re-synthesis experiments, which showed that the three isolates colonised root tissues of poplar plantlets whereas two of them formed microsclerotia-like structures. Taken together, these results suggest an endophytic lifestyle of these isolates. This is the first evidence of S. vermifera as a root endophyte of poplar. A new endophytic putative species belonging to the Helotiales and closely related to Leohumicola is also reported. Interestingly, and when compared to mock-inoculated plants, both P06 and P04 isolates increased the number of root tips of inoculated poplar plantlets in vitro. Moreover, the S. vermifera P04 isolate also increased the shoot biomass. The results are discussed in relation to the potential use of endophytic strains for tree-based phytoremediation of metal-contaminated sites.

Evaluation of soil microbial communities as influenced by crude oil pollution

Impact of petroleum pollution in a vulnerable Niger Delta ecosystem was investigated to assess interactions in a first-generation phytoremediation site of a crude oil freshly-spilled agricultural soil. Community-level approach for assessing patterns of sole carbon-source utilization by mixed microbial samples was employed to differentiate spatial and temporal changes in the soil microbial communities. Genetic diversity and phenotypic expressions were measured for a more holistic perspective. The 5’- terminal restriction fragments generated after Csp digestion of 16S rRNA gene correlated with observed DNA concentrations in the community profile and revealed loss of diversity with pollution. Crude oil pollution significantly reduced phosphomonoesterases and respiratory activities and values were pH dependent. There were no expressed dehydrogenases activity in initial spill site but were enhanced with phytoremediation. Factor analysis of predictors and independent variables indicates that respiratory, alkaline phosphatase and â-glucosidase activities could be used to explain underlying factors. Positive soil – microbes - plant interactions were observed. Key words : Species diversity, impact of crude oil pollution, soil – biota interactions, ecosystem monitoring, genetic diversity.

Volatilization of Trichloroethylene from Trees and Soil: Measurement and Scaling Approaches

Trichloroethylene (TCE) volatilization from leaves, trunk, and soil was measured to assess the significance of these pathways from phytoremediation sites at Travis and Fairchild Air Force Bases. Measurements were scaled temporally and spatially to estimate the annual volatilization of TCE at the Travis (0.82 ± 0.51 kg/yr) and Fairchild sites (0.014 ± 0.008 kg/yr). Volatilization was primarily through the leaf (0.34 ± 0.16 kg/yr at Travis and 0.01 ± 0.06 kg/yr at Fairchild) and soil (0.48 ± 0.36 kg/yr at Travis, 0.003 ± 0.002 kg/yr at Fairchild) pathways. The larger volatilization estimate at Travis was expected because of the site's higher TCE groundwater concentrations. Using groundwater data collected in 2004 and 2009, calculations show that over the 5 year period, 1.7 and 0.015 kg of TCE were removed each year at the Travis and Fairchild sites, respectively. On the basis of the scaled field measurements, volatilization from the leaves and soil may play a significant role in TCE removal at both sites. Daily and seasonal variations were not addressed during the limited daytime sampling events, but the methods described here provide a novel and practical framework for evaluating the potential importance of volatilization of TCE and similar compounds at phytoremediation sites.

A solid-phase microextraction method for the in vivo sampling of MTBE in common reed (Phragmites australis)

Phytoscreening of phytoremediation-based plantings is discussed as a promising monitoring tool in literature. We developed and applied an analytical procedure for the in vivo sampling of methyl tert-butyl ether (MTBE) in the common reed (Phragmites australis) from a phytoremediation site highly polluted with MTBE. The approach uses solid-phase microextraction (SPME) with the SPME fibre directly introduced into the aerenchyma of the plant stem. For optimising the analytical procedure and estimating the capability of the proposed method, laboratory tests on the microcosm scale and field studies over one vegetation period were carried out. Furthermore, the results of in vivo SPME sampling were compared with those obtained with the traditional approach for analysing plants using dynamic headspace analysis. The MTBE signals detected within the plants were also correlated with the concentration in the water phase. The discussion of results showed the feasibility of the proposed method for a qualitative phytoscreening of volatile organic compounds present in wetland plants.

NATIVE MICHIGAN PLANTS STIMULATE SOIL MICROBIAL SPECIES CHANGES AND PAH REMEDIATION AT A LEGACY STEEL MILL

A 1.3-acre phytoremediation site was constructed to mitigate polyaromatic hydrocarbon (PAH) contamination from a former steel mill in Michigan. Soil was amended with 10% (v/v) compost and 5% (v/v) poultry litter. The site was divided into twelve 11.89 m X 27.13 m plots, planted with approximately 35,000 native Michigan perennials, and soils sampled for three seasons. Soil microbial density generally increased in subplots of Eupatorium perfoliatum (boneset), Aster novae-angliae (New England aster), Andropogon gerardii (big bluestem), and Scirpus atrovirens (green bulrush) versus unplanted subplots. Using enumeration assays with root exudates, PAH degrading bacteria were greatest in soils beneath plants. Initially predominant, Arthrobacter were found capable of degrading a PAH cocktail in vitro, especially upon the addition of root exudate. Growth of some Arthrobacter isolates was stimulated by root exudate. The frequency of Arthrobacter declined in planted subplots with a concurrent increase in other species, including secondary PAH degraders Bacillus and Nocardioides. In subplots supporting only weeds, an increase in Pseudomonas density and little PAH removal were observed. This study supports the notion that a dynamic interplay between the soil, bacteria, and native plant root secretions likely contributes to in situ PAH phytoremediation.